Chapter 1 and Intro to casting Flashcards Preview

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Flashcards in Chapter 1 and Intro to casting Deck (19):
1

Definition of Manufacturing

A well organized method of converting raw material to an end product that has value and utility

2

Casting

liquid material is poured into a mold allowing for solidification of the desired shape

3

Forming and Shaping

Uses stresses (like compression, tension, shear) to plastically deform the material to the desired shape

4

Machining

process of removing material from a workpiece using power-driven machine tools

5

Joining

*welding* two or more parts are melted and forced together

6

Finishing

performed after the part is formed
-Alters the surface of the part to achieve certain properties

7

Fundamentals of High Quality Production with:

-Good surface finish
-Dimensionally accurate
-Good Strength
-Lack of defects

1) Solidification of metal and accompanying shrinkage

2) Flow of the molten metal into the mold cavity

3) Heat transfer during solidification and cooling of the metal in the mold

4) Mold Material and its influence on the casting operations

8

Solidification of Pure Metals

Pure metals have clearly defined melting and freezing points

Solidification takes place at constant temperature

Contracts when it cools changing the density

9

Solidification of Alloys

Alloys solidify over a range of temperatures (mushy/paste state)

Phase diagrams graphically illustrate the relationship between phase and temperature and composition of material

10

Purpose of the Riser

-"Cavity is full" verified
-gases escape
-reinforcement for metal shrinkage

11

What are hot spots?

Sections of the casting that will solidify last

12

Proper Fluid flow will minimize these three variables

-premature cooling
-turbulence
-gas entrapment

13

Sprue Geometry

Tapers in to prevent aspirations (gap between fluid and wall allowing for air to get into the fluid)

14

Critical Reynolds number

Over 20,000 represents severe turbulence resulting in air entrapment

15

What is Fluidity

The ability of the molten metal to fill mold cavities

16

Characteristics that Influence Fluidity

-Viscosity (decreases fluidity)
-Surface tension (reduces fluidity)
-Inclusions
-Shorter solidification range of pure metals give higher fluidity
-Alloys with longer freezing ranges have lower fluidity

17

Casting parameters that effect fluidity

-Mold design (sprue runners etc..)
-Mold material (higher thermal conductivity of mold lowers fluidity)
-Rate of Pouring (lower rate of pouring the lower the fluidity)
-Heat transfer affects viscosity and therefore affects fluidity

18

Chvorinov's Rule
(Solidification time)

solidification time = C *(volume/Surface Area)^(n)

-C is a constant related to material properties
-n is usually 2

19

Shrinkage

Caused by:
-Contraction of molten metal as it cools
-Contraction during phase change (largest potential amount of shrinkage)
-Contraction as metal cools to room temperature